Other 18th-century logicians

Lambert also developed a method of pictorially displaying the overlap of the content of concepts with overlapping line segments. Leibniz had experimented with similar techniques. Two-dimensional techniques were popularized by the Swiss mathematician Leonhard Euler in his Lettres à une princesse d’Allemagne (1768–74; “Letters to a German Princess”). These techniques and the related Venn diagrams have been especially popular in logic education. In Euler’s method the interior areas of circles represented (intensionally) the more basic concepts making up a concept or property. To display “All A’s are B’s,” Euler drew a circle labeled “A” that was entirely ... (100 of 29,044 words)